Smart distribution network: The grid of the future

Project state

Started

Whether wind or solar, the market share of electricity generated from renewable energy sources is growing in Germany. This burdens the distribution networks. They were designed to transport electricity from the power plants to the consumers – in one direction and only in the amount needed. The process has now changed because of the energy transition and decentralised electricity generation systems: on sunny days, solar power systems produce more electricity than the residents of some regions can consume, causing distribution networks to hit their load limits.

Approaches from individual projects to be developed holistically

What do these changes entail in detail? What are the short and medium-term solutions for grid operators? Which smart solutions could help adapt the grids to the new circumstances, allowing them to continue working reliably around the clock even in critical situations? This is the question that researchers are exploring in the “grid-control” project. They are developing procedures, concepts and infrastructures for stable grids that increase the cost-effectiveness and resource efficiency of the energy supply system. For a period of three years, a consortium of partners from academia and the industry are seeking solutions for sustainable distribution grids. In grid-control, the partners draw upon results of previous projects and merge their approaches to form a holistic concept, which they then further develop in a meaningful way. Nine partners are contributing their expertise to this project. Practical findings are provided by tests carried out in Energy Smart Home Lab of the Karlsruhe Institute of Technology (KIT), and in NETZlabor of Netze BW.

Interaction between generators, consumers and smart systems

One aim of the project: the interaction between the technical systems of grid operators, energy market participants and end-users. The mechanisms to be explored ensure the stable operation of distribution grids and the integration of additional distributed generation in the medium and low voltage grids.

Stable grid operation load requires reliable load and feed-in forecasts. They allow the prediction of grid bottlenecks. Since more and more flexibility potentials will be utilised by energy market participants in the future, grid operators must consider them in the creation of load flow forecasts. For this, the researchers are developing a Grid Load Management System. It provides an interface between energy market participants and the grid operator. In addition to the creation of load flow forecasts, this software solution would regulate the utilisation of the limited grid capacity in advance.

A regional energy management system for decentralised control is being developed for grid operators. It represents a decentralised level underneath the grid control system and communicates with generators and sensors in the distribution grid. The energy management system is to make system-critical states easier to control, monitor the grid state and during limit violations, it will act on plants causing the bottlenecks to ensure reliable grid operation. The traffic light concept of BDEW forms the basis of the entire solution that links the systems of distribution grid operators, external market participants and customers.

The local coordination of generators, battery storage systems and consumers, such as electric vehicles, is already partially accomplished by energy management systems. In the future, many such solutions will take over the tasks that will be embedded in the currently emerging smart meter infrastructure. The project employs building energy management systems in conjunction with battery storage systems for a multi-role use of these flexibility potentials. They are integrated in the overall concept with the Grid Load Management System and the Regional Energy Management Systems.

Provision of ancillary services

This map of Baden-Wuerttemberg shows where the laboratory tests and field trials during the research project “grid-control” take place. | Image: NetzeBW

The overall number of conventional power plants is dropping as part of the energy transition. However, they are responsible for covering the need for ancillary services that are necessary for stable grid operation. The German Energy Agency (dena) predicts a lack of reactive power and instantaneous reserve as of 2030. Therefore, the researchers are developing alternative solutions for the provision of ancillary services by the distribution grids. To date, the dimensioning of the capacity of distribution grids follows a deterministic planning method that estimates the expected maximum load and feed-in. A probabilistic planning method is under development in order to operate economically in spite of the changing needs of distribution grids.

At present, it is uneconomical to use sensors to detect the grid state in the distribution grids. In order to observe the load flows in the grid in real-time, this will be necessary in the future, however. When limit values are exceeded, operators could then intervene quickly using distributed automation systems. To observe the grid state, the project is currently building an optimised and efficient process for state estimation based on data provided by the future smart meter infrastructure.

Development and evaluation of the overall system is taking place in several steps. First, the functions and interfaces of the individual solutions are defined. Then, the system solutions are developed and tested in an extensive laboratory test at KIT and NETZlabor of Netze BW. Results of the first steps of the project are expected in 2016.